1. Field of the Invention
The invention relates to a plasma device, and more particularly, to an atmospheric plasma device.
2. Description of Related Art
With the development of plasma technology, atmospheric arc plasma in the plasma has been widely applied to various fields of surface treatment. For example, the atmospheric arc plasma may be used to perform a surface treatment to an object to be treated, so as to enhance a reliability for performing a process, such as adhering, printing, packaging or epitaxizing, on a surface of this object. However, as being restricted by negative resistance characteristics of an electric arc, a process range of this type of atmospheric arc plasma is limited, and thus is unable to simultaneously produce a large area arc discharge. Although a discharge density of the atmospheric arc plasma is relatively higher and causes more active substances to be produced by this plasma technique, so that a speed of the plasma treatment may be raised (it requires only a short amount of time to complete the surface treatment for a scanning area), large area arc discharge characteristic is unable to be produced, and thus the application of this type of atmospheric arc plasma is still being limited.
In order to improve the applicability of the atmospheric arc plasma, U.S. Pat. No. 6,262,386 and TW Patent No. M426456 each discloses a plasma device, wherein an arc plasma nozzle titles an angle in relative to an axis of the plasma device, and the nozzle may rotate circumferentially around the axis so as to increase an ejection area of the plasma, thereby attaining an effect of large area surface treatment. However, at the same time of rotating the nozzle to expand the effective surface area of the plasma treatment, it is required to supply the plasma device with more power, so that enough amount of the required plasma may be produced. However, as high power is being applied, a temperature of the plasma also rises and thereby influences the performance of the plasma in performing the surface treatment to the object being treated, especially for heat sensitive objects, such as flexible substrate and so forth. Therefore, how to retain the performance of the plasma treatment while controlling the temperature of a substrate is one of the issues that have to be conquered in the field of plasma device. Moreover, in addition to the problem of unable to effectively lower the temperature of the plasma, a rod-shaped inner electrode as disclosed by U.S. Pat. No. 6,262,386 is also apt to be damaged due to the plasma being concentrated on a single point, especially when high power is being applied, and thereby influences a reliability of the device.